It is common to use a graphics tablet (digitizer) as an input device for a variety of applications. Not only are coordinates entered as data to be processed in their own right, but it is frequently convenient to use the stylus to control the various modes of operation available within the application. This may be accomplished by digitizing points within icons visible on a menu upon the tablet. Since menus may become worn or be misplaced, it is also common for a software application package to provide for the plotting of replacement menus as needed. The size of paper used by the user in plotting a new menu may well depend upon the user's cultural setting. One way to allow this variability is to require the user to digitize the coordinates of diagonal corners of the new menu. This allows the software application package to determine where on the table the menu lies. It would be desirable to free the user from such a requirement, which could be done if it were arranged that the icons of the menu were always in a fixed location upon the tablet, regardless of the paper size.
Ensuring that the icons of a menu plotted by the application software at the behest of the user are always located at the same place upon the tablet can be accomplished as follows. First, the plotting process is made responsive to the size of paper being used. Some plotters, for example, actually find the corners of the paper at the start of the plotting process. Other plotters require that the user move the pen to two or more corners of the paper. Either way, if the sheet of paper is of a standard size (e.g., one of the ANSI sizes or one of the ISO sizes) the software can arrange that the menu be plotted onto the paper with a corresponding selected offset from a reference location on the sheet (e.g., the lower left corner). Second, it is arranged that each size of paper be automatically registered in a selected corresponding location upon the tablet. The corresponding locations are selected such that, for each size of paper upon which a menu is plotted, there obtains for each icon in the menu a constant (x, y) offset between those icons and the origin of the tablet. In a preferred embodiment each standard size sheet of paper is automatically registered by its fitting with a corresponding portion of a recess in the surface of the tablet. Each size of paper interlocks with its corresponding portion of the recess, and with no other, with the result that each size sheet is registered in a position upon the tablet associated with that size. All four corners of the paper engage the recess, with the further result that the sheet is not only registered, but also restrained from sliding about. A cover sheet of mylar also matches and fits into the entire recess, and serves to protect the menu. In this way the user can create a menu upon any standard size paper recognized by the software and matched by the recess, put the menu onto the tablet such that it is engaged by the appropriate corners of the recess, and proceed to use the menu without further instruction to the software application concerning where the menu actually ended up upon the tablet. This obtains because the menu automatically ends up where the software, by design, expects it to be.